No abstract

To investigate key taste-active components in Takifugu obscurus (T. obscurus), twenty-eight putative taste compounds in cooked muscle of T. obscurus were quantitatively analyzed and the pivotal components were identified by taste reconstitution, omission and addition tests. Moreover, the role of flavor peptides in overall taste profile of T. obscurus were evaluated. Sensory evaluation revealed that glutamic acid, serine, proline, arginine, lysine, adenosine-5´-monophosphate, inosine-5´-monophosphate (IMP), succinic acid, sodium, potassium, phosphates and chlorides, were the core taste-active contributors to T. obscurus. Besides glutamic acid, IMP, succinic acid and potassium, the characteristic T. obscurus-like umami and kokumi profiles were induced by adding flavor peptides, among which Pro-Val-Ala-Arg-Met-Cys-Arg and Tyr-Gly-Gly-Thr-Pro-Pro-Phe-Val were identified as key substances on the basis of addition test and dose-response analysis.The present data may help to reveal the secret of delicious taste of T. obscurus and provide the basis for development of deeper flavor analysis of pufferfish.

Taste peptides, as an important component of protein-rich foodstuffs, potentiate the nutrition and taste of food. Thereinto, umami-and bitter-taste peptides have been ex tensively reported, while their taste mechanisms remain unclear. Meanwhile, the identification of taste peptides is still a time-consuming and costly task. In this study, 489 peptides with umami/ bitter taste from TPDB (http://tastepeptides-meta.com/) were collected and used to train the classification models based on docking analysis, molecular descriptors (MDs), and molecular fingerprints (FPs). A consensus model, taste peptide docking machine (TPDM), was generated based on five learning algorithms (linear regression, random forest, gaussian naive bayes, gradient boosting tree, and stochastic gradient descent) and four molecular representation schemes. Model interpretive analysis showed that MDs (VSA_EState, MinEstateIndex, MolLogP) and FPs (598, 322, 952) had the greatest impact on the umami/bitter prediction of peptides. Based on the consensus docking results, we obtained the key recognition modes of umami/bitter receptors (T1Rs/T2Rs):(1) residues 107S-109S, 148S-154T, 247F-249A mainly form hydrogen bonding contacts and (2) residues 153A-158L, 163L, 181Q,

Umami taste receptor type 1 member 1/3 (T1R1/T1R3) heterodimer has multiple ligand-binding sites, most of which are located in T1R1-Venus flytrap domain (T1R1-VFT). However, the critical binding process of T1R1-VFT/umami ligands remains largely unknown. Herein, T1R1-VFT was prepared with a sufficient amount and functional activity, and its binding characteristics with typical umami molecules (monosodium l-glutamate, disodium succinate, beefy meaty peptide, and inosine-5′-monophosphate) were explored via multispectroscopic techniques and molecular dynamics simulation. The results showed that, driven mainly by hydrogen bond, van der Waals forces, and electrostatic interactions, T1R1-VFT bound to umami compound at 1:1 (stoichiometric interaction) and formed T1R1-VFT/ligand complex (static fluorescence quenching) with a weak binding affinity (K a values: 252 ± 19 to 1169 ± 112 M–1). The binding process was spontaneous and exothermic (ΔG, −17.72 to −14.26 kJ mol–1; ΔH, −23.86 to −12.11 kJ mol–1) and induced conformational changes of T1R1-VFT, which was mainly reflected in slight unfolding of α-helix (Δα-helix < 0) and polypeptide chain backbone structure. Meanwhile, the binding of the four ligands stabilized the active conformation of the T1R1-VFT pocket. This work provides insight into the binding interaction between T1R1-VFT/umami ligands and improves understanding of how umami receptor recognizes specific ligand molecules.